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Adaptation to cold and depth: contrasts between polar and deep-sea animals
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- By G.N. Somero
- Edited by Hans-O. Pörtner, Alfred-Wegener-Institut für Polar-und Meeresforschung, Bremerhaven, Germany, Richard C. Playle, Wilfrid Laurier University, Ontario
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- Book:
- Cold Ocean Physiology
- Published online:
- 13 March 2010
- Print publication:
- 28 March 1998, pp 33-57
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Summary
Two regions of the world ocean are characterised by extremely cold temperatures: the polar oceans and the deep sea. In each of these regions, water temperatures usually are close to 0°C. In the polar oceans, especially in the waters surrounding Antarctica, temperatures may rise seasonally by no more than a few hundredths of a degree centigrade above the freezing point of sea water, −1.86°C (Eastman, 1993). Deep-sea temperatures generally are also very stable, with the notable exception of waters found at the deep-sea hydrothermal vents, where animals may encounter temperatures between approximately 2°C and at least 40°C (Fustec, Desbruyeres & Juniper, 1987; Johnson, Childress & Beehler, 1988; Dahlhoff et al, 1991). Thus, ectothermic species living in polar and typical deep-sea waters are characterised by some of the lowest and most stable body temperatures found in any species, in any environment. One would predict that many physiological and biochemical systems of shallow-living polar species and deep-sea species would manifest similar adaptations to low and stable temperatures.
Despite facing similar thermal conditions, deep-sea species and shallowliving polar species encounter other environmental differences that may lead to divergent patterns of adaptation. Hydrostatic pressure is one important difference between shallow and deep cold water habitats. Pressure rises by approximately 0.1 MPa (∼1 atm) with each 10 m increase in depth, so deepliving organisms encounter pressures of up to 100 MPa (=∼1000 atm) in the deepest trenches of the ocean. Because most physiological and biochemical systems are sensitive to pressure (Siebenaller, 1991; Somero, 1993), adaptations to high pressure, as well as to low temperature, would be expected to characterise diverse physiological and biochemical traits of deep-sea species.
Stenotherms and eurytherms: mechanisms establishing thermal optima and tolerance ranges
- Edited by Ian A. Johnston, University of St Andrews, Scotland, Albert F. Bennett, University of California, Irvine
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- Book:
- Animals and Temperature
- Published online:
- 04 May 2010
- Print publication:
- 10 October 1996, pp 53-78
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Summary
Introduction
Enormous differences exist among ectothermic animals in optimal body temperatures and breadth of thermal tolerance ranges. Extreme stenothermy, coupled with cold tolerance, is exemplified by highly coldadapted notothenioid fishes of Antarctica, that have a thermal tolerance range of only about 6 °C (from the freezing point of seawater, –1.86 °C, to approximately 4 °C; Somero & DeVries, 1967; Eastman, 1993). In contrast, extreme eurythermy and heat tolerance is exhibited by fishes such as the intertidal goby Gillichthys seta, whose body temperature may range from approximately 8 °C to 40 °C, as a function of both seasonal and diurnal changes in water temperature (Dietz & Somero, 1992). The physiological, biochemical and molecular mechanisms that distinguish stenotherms and eurytherms are likely to play critical roles in establishing biogeographical patterning and in establishing the susceptibility of animals to shifts in ambient temperature, such as are predicted as a consequence of global warming.
This review compares homologous biochemical and physiological systems in stenotherms and eurytherms, and relates interspecific differences in these systems to the thermal optima and tolerance ranges characteristic of the whole organism. In keeping with a central theme of this symposium, namely, the similarities and differences found between evolutionary adaptation to temperature and short-term phenotypic acclimatisation, this review contrasts genetically-fixed traits that are important in setting thermal limits and thermal optima, with more ‘plastic’ traits that provide significantly different phenotypes under different thermal conditions.